ELECTRON-RICH AROMATICS .I. SOLVOLYSIS OF 1-ARYLETHYL ACETATES

Solvolysis rates for a series of 1-arylethyl acetates have been determined in 30% ethanol. Rates for phenyl groups with para substituents (hydrogen, methyl, phenoxy, methoxy, N-methylanilino, and N,N-dimethyl-amino) correlate well with σ+, ρ = –5.70. From rate constants for heteroaromatic compounds, the following σ+ constants have been derived (based 0n the substituent constant for the entire aryl group): 2-thienyl, –0.84; 3-thienyl, –0.47; 5-methyl-2-thienyl, –1.17; 5-bromo-2-thienyl, –0.70; 2-benzothienyl, –0.43; 3-benzothienyl, -0.52; 2-furyl, -0.94; 3-furyl, -0.49; 5-methyl-3-furyl, -1.34; 2-benzofuryl, -0.47; 3-benzofuryl, -0.46; l-methyl-2-pyrrolyl, -1.96; l-methyl-2-indolyl, -1.16; l-methyl-3-indolyl, -1.98; 9-ethyl-3-carbazolyl, -1.13; ferrocenyl, -1.55. Protodesilylation rates of Eaborn are found to correlate well with the present σ+ values. Comparisons with other literature data are discussed. © 1969, American Chemical Society. All rights reserved.